Ominous odors: olfactory control of instinctive fear and aggression in mice.

Aggression and fear are often thought to be distinct behavioral states, yet they share several common output responses. In the mouse, both can be initiated by specialized odor cues. How these cues signal through the olfactory system to promote behavior is largely unknown. Recent experiments have started to uncover the relevant signaling ligands, chemosensory receptors, and responsive sensory neurons that together enable the precise manipulation of behaviorally relevant neural circuits. Moreover, the use of molecular genetics and new experimental strategies has begun to reveal how the central nervous system processes olfactory information to initiate aggression and fear. A sensory-initiated comparative study of these two fundamental threat reactions promises to offer new mechanistic insight.